//binary to decimal 
#include<iostream>
using namespace std;

int DecToBinary(int n ){
    int p=1;
    int ans =0;
    int last_digit;
    while (n!=0){
            last_digit= n%10;
            ans= ans + last_digit*p; 
            n=n/10;
            p=p*2;
                    }

    return ans;
}


int main(){
    int N;
    cin>>N;
    cout<<DecToBinary(N)<<endl;



    return 0;
}